Device for water supply

ABSTRACT

The purpose of the present invention is to provide a tool for water supply, which has luster and rarely undergoes the leaching out of nickel. A tool for water supply  100  which is provided with a nickel-plated layer  102  formed on a base material  101 , wherein the nickel-plated layer  102  contains no sulfur component, the corrosion potential of the nickel-plated layer  102  in a leaching solution as measured against a saturated calomel electrode is −0.01 or more (preferably +0.04 V or more), and the Wa value of the nickel-plated layer  102  as measured using a WaveScan device manufactured by BYK is 5.1 or less.

TECHNICAL FIELD

The present invention relates to a technique to reduce leaching ofnickel from a device for water supply including a nickel plating layerformed on a base material.

BACKGROUND ART

Conventionally, devices for water supply that are used as a kitchenfaucet, a laboratory faucet, a bath faucet, and other similar devicesare made of, for example, a copper alloy from the viewpoints ofcorrosion resistance, processability, machinability, etc. This type ofdevice for water supply is produced through a process in which arough-formed copper alloy piece is cut and ground to be formed into abase material, and nickel plating is provided on the outer peripheralsurface of the base material. In some cases, chrome plating is alsoprovided on the nickel plating.

As shown in FIG. 3, in the vicinity of an opening of such a device forwater supply provided with nickel plating, the nickel plating layer mayalso be deposited on the inner surface of the device for water supply soas to have an overlay portion due to throwing power. Even if chromeplating is provided on the device for water supply, the chrome platingis unlikely to be deposited on the inner surface. Referring to thedevice 100 for water supply shown in FIG. 3, when the base material 101comes into contact with water, nickel not only leaches from the basematerial 101 (which often contains nickel intentionally added for thepurpose of increasing corrosion resistance or nickel as an unintentionalimpurity), but also from the overlay portion of the nickel plating layer102.

Specifically, as shown in FIG. 4, an analysis of components of a crosssection of an opening of a known device for water supply provided withnickel plating has demonstrated the following. In a region inwardlydistant by more than 15 mm from the end face of the opening (innerregion of the device for water supply), the principal component (copper)of the base material 101 is detected at a high ratio, whereas negligiblenickel is detected. On the other hand, in a region inwardly extendingover a distance of less than 15 mm from the end face of the opening(region close to the opening of the device for water supply), nickelleaching from the overlay portion is detected at a high ratio.

In view of this, a technique is proposed to reduce an amount of nickelleaching from nickel plating provided on a device for water supply (inparticular, the overlay portion) (see, for example, Patent Document 1).According to the technique disclosed in Patent Document 1, a sulfurcomponent-containing organic additive is added to the nickel plating toimpart gloss to the device for water supply, while chloral hydrate isadded to reduce an amount of nickel leaching into tap water. Accordingto this technique, chloral hydrate is added to a nickel platingprocessing solution to which the sulfur component-containing organicadditive has been added, so that the nickel plating has a noblepotential and the amount of nickel leaching from the nickel plating isreduced.

Meanwhile, water quality that tap water needs to maintain is determinedby an Ordinance of the Ministry of Health, Labour, and Welfare, pursuantto the Water Supply Law. “Ministerial Ordinance on Water QualityStandards” enforced on Apr. 1, 2015 provides items of water qualitystandards and standard values (51 items). The Ministerial Ordinance alsoprovides target-setting items for water quality management and targetvalues (26 items), as a target of water quality that tap water shouldmaintain. Nickel constitutes one item of the target-setting items forwater quality management, and its target value is set to 0.02 mg/L.

The target values for water quality management provided in theMinisterial Ordinance are predicted to be regarded as water qualitystandards required for potable water. In this case, it will be requiredthat an amount of nickel (a leaching value of nickel) contained inpotable water discharged from a device for water supply be not more thanone-tenth of the value defined in the target-setting item for waterquality management. The same or similar measures will be needed for tapwater other than potable water.

-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. 2015-212417

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the nickel plating (hereinafter also referred to as “glossnickel plating”) disclosed in Patent Document 1, to which the sulfurcomponent-containing organic additive is added, can reduce an amount ofleaching nickel to a limited extent. On the other hand, use of nickelplating to which no sulfur component-containing organic additive isadded (hereinafter also referred to as “semigloss nickel plating”) canreduce an amount of leaching nickel, while making it difficult to attainsufficient gloss.

It is an object of the present invention to provide a device for watersupply which is glossy and from which a small amount of nickel leaches.

Means for Solving the Problems

The present invention related to a device for water supply including anickel plating layer formed on a base material. The nickel plating layercontains no sulfur component. A corrosion potential of the nickelplating layer in a leach test liquid is −0.01 V or greater with respectto a saturated calomel electrode as a reference. A surface of the nickelplating layer has a Wa value of 5.1 or less.

The corrosion potential of the nickel plating layer in the leach testliquid is preferably +0.04 V or greater with respect to the saturatedcalomel electrode as the reference.

Effects of the Invention

The present invention provides a device for water supply which is glossyand from which a small amount of nickel leaches.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a device for water supply accordingto the present embodiment;

FIG. 2 is an exploded view of the device for water supply according tothe present embodiment;

FIG. 3 is a schematic cross-sectional view illustrating a structure ofthe vicinity of an opening of the device for water supply according tothe present embodiment;

FIG. 4 is a graph showing detection ratios of metals at an inner surfaceof an opening of a known device for water supply;

FIGS. 5A and 5B show representative results of analyses of Examples andComparative Examples using an EPMA;

FIGS. 6A and 6B shows, on an enlarged scale, sulfur peaks in FIGS. 5Aand 5B;

FIG. 7 shows a relationship between an appearance of a nickel platinglayer and a Wa value (measured with WaveScan of BYK Japan KK) of asurface of the nickel plating layers of Examples and ComparativeExamples;

FIG. 8 shows potential-current curves and Ni leaching values ofrepresentative plating layers in a leach test liquid; and

FIG. 9 shows a relationship between a corrosion potential and a nickelleaching value of representative nickel plating layers in a leach testliquid.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will be described withreference to the drawings. Note that the present invention is notlimited to the following embodiment.

First, a faucet produced by combining devices for water supply accordingto the present embodiment will be described as an example. FIG. 1 is aschematic view showing the faucet according to the present embodiment.FIG. 2 is an exploded view of the faucet according to the presentembodiment. As shown in FIGS. 1 and 2, the faucet 1 according to thepresent embodiment is a common faucet (e.g., a kitchen faucet, alavatory faucet, or a bath faucet) and configured to discharge tap waterfrom a spout 30. The faucet 1 includes a body 10, legs 20, and handles50. In the present specification, the term “device for water supply” hasa meaning encompassing not only faucet parts such as a tap and a valvefor supplying potable water, but also a joint and a water supply pipe.The “devices for water supply” are classified into “end-use water supplydevices”, “water supply pipes”, “water supply devices disposed at middlepositions of piping”, etc. The term “device for water supply” as usedherein encompasses all of these devices and pipes. Structurallyspeaking, the “device for water supply” has an internal channel throughwhich water passes and an exterior surface which does not contact withwater. The present invention can be favorably provided as a faucet part.

The body 10 is an example of the devices for water supply connectable tovarious devices for water supply. The body 10 includes a threadedportion 12 connectable to the leg 20, a threaded portion 13 connectableto the spout 30, and a threaded portion 14 connectable to the handle 50via a spindle 40.

The leg 20 is an example of the devices for water supply connectable tothe body 10. The leg 20 has one end connected to a tap water supplysource (not shown). The other end of the lag 20 has a nut 21 attachedthereto. The nut 21 of the leg 20 is screwed onto the threaded portion12 of the body 10, so that the leg 20 is connected to the body 10.

The spout 30 is an example of the devices for water supply connectableto the body 10. One end of the spout 30 has a nut 31 attached thereto,and the other end has an end sleeve 32 attached thereto. The nut 31 ofthe spout 30 is screwed onto the threaded portion 13 of the body 10, sothat the spout 30 is connected to the body 10.

The handle 50 is a part for adjusting a flow rate of water to bedischarged. One end of the spindle 40 is attached to the handle 50. Theother end of the spindle 40 is screwed onto the threaded portion 14 ofthe body 10, so that the handle 50 is connected to the body 10 via thespindle 40.

The body 10, the leg 20, the nut 21, the spout 30, the nut 31, the endsleeve 32, and the spindle 40 include a base material 101 and a nickelplating layer 102 formed on an outer peripheral surface of the basematerial 101. In the present embodiment, the body 10, the leg 20, thenut 21, the spout 30, the nut 31, and the end sleeve 32 include a chromeplating layer 103 formed on the nickel plating layer 102. The body 10,the leg 20, the spout 30, and other components have undergone leadremoval treatment as necessary.

Next, the device for water supply according to the present embodimentwill be described. FIG. 3 is a schematic view illustrating a structureof the device for water supply according to the present embodiment,specifically, a cross-sectional structure of an opening of the body 10as the device for water supply. FIG. 4 is a graph showing detectionratios of metals at an inner surface of an opening of a known device forwater supply.

As shown in FIG. 3, the device 100 for water supply according to thepresent embodiment includes the nickel plating layer 102 formed on thebase material 101. In the opening of the device 100 for water supply,the nickel plating spreads to reach the water channel so as to have anoverlay portion due to throwing power. In the device 100 for watersupply having this configuration, when water flows in an F1 direction,nickel leaches not only from the base material 101, but also from theoverlay portion of the nickel plating layer 102.

As shown in FIG. 4, conventionally, the amount of nickel leaching fromthe base material 101 is less than the amount of nickel leaching fromthe overlay portion of the nickel plating layer 102. Therefore, areduction in the leaching of nickel from the device 100 for water supplyrequires a reduction in the leaching of nickel from the overlay portionof the nickel plating layer 102. It would be conceivable to provide thechrome plating layer 103 on the nickel plating layer 102. However, sincethe chrome plating layer 103 is unlikely to spread inward and does notcontain nickel, the presence or absence of the chrome plating layer 103has a small effect on the leaching of nickel.

In the present embodiment, the base material 101 is made of, forexample, a copper alloy. The nickel plating layer 102 is a layer formedon the base material 101. The nickel plating layer 102 is formed on thebase material 101 by using, for example, a plating solution having thecomposition and condition described below. The chrome plating layer 103may be provided on the nickel plating layer 102.

A basic composition of the nickel plating solution, which is theso-called Watts solution, includes nickel ions, chloride ions, sulfateions, and boric acid. Specifically, the basic composition includes, forexample, 50 g/L of NiCl₂.6H₂O, 290 g/L of NiSO₄.6H₂O, and 40 g/L ofH₃BO₃. The plating is formed under the conditions of a pH of about 4.0and a temperature of about 55° C. As organic additives, sulfur-freesalicylic acid, hexynediol, butynediol, propargyl alcohol, chloralhydrate, etc. can be used.

The plating solution described above is free of sulfur-containingorganic additives (e.g., saccharin). Consequently, the nickel platinglayer 102 of the present embodiment contains no sulfur. This featurereduces leaching of nickel from the nickel plating layer 102. In thepresent specification, “a nickel plating layer contains no sulfur”refers to a case where sulfur is not detected in an elementary analysisusing an EMPA (e.g., an analysis method to be described later) performedon the nickel plating layer.

Further, if the nickel plating layer that has been formed using theabove-described plating solution has a corrosion potential of +0.04 V orgreater with respect to a saturated calomel electrode (SCE) in a leachtest liquid, the amount of nickel leaching into tap water from thedevice for water supply can be reduced to no more than one-tenth of thevalue defined in the target-setting item for water quality management.

Specifically, when 0.8 g/L or more (preferably 0.9 g/L or more) ofchloral hydrate is added to the plating solution, the nickel platinglayer 102 has a noble potential, and the leaching of nickel from thenickel plating layer 102 is further reduced. On the other hand, when theamount of chloral hydrate contained in the plating solution is less than0.8 g/L, it is difficult to reduce the leaching of nickel by the chloralhydrate alone.

Further, use of the plating solution described above makes the nickelplating layer have a Wa value of 5.1 or less as measured with WaveScanmanufactured by BYK Japan KK. As a result, the surface of the device 100for water supply (the surface of nickel plating layer 102) is providedwith gloss. Specifically, addition of 0.8 g/L to 1.75 g/L of chloralhydrate to the plating solution makes the surface of the device 100 forwater supply glossy. On the other hand, when the amount of chloralhydrate in the plating solution exceeds 1.75 g/L, the surface of thedevice 100 for water supply becomes tarnished. Note that in the presentspecification, the Wa value is measured with the WaveScan manufacturedby BYK Japan KK.

As can be seen, by a production method including forming plating on thebase material 101 using a nickel plating processing solution that isfree of sulfur-containing organic additives and contains chloral hydratein an amount of 0.8 g/L to 1.75 g/L, the device 100 for water supply canbe produced which is glossy and from which a small amount of nickelleaches.

The present embodiment exerts the following effects. The device forwater supply according to the present embodiment is configured as thedevice 100 for water supply including the nickel plating layer 102provided on the base material 101. The nickel plating layer 102 containsno sulfur. A corrosion potential of the nickel plating layer 102 in theleach test liquid is −0.01 V or greater with respect to a saturatedcalomel electrode as a reference. A surface of the nickel plating layer102 has a Wa value (as measured with the WaveScan manufactured by BYKJapan KK) of 5.1 or less. This feature enables provision of the device100 for water supply which is glossy and from which a small amount ofnickel leaches.

The corrosion potential of the nickel plating layer in the leach testliquid is preferably +0.04 V or greater with respect to the saturatedcalomel electrode as the reference. This feature makes it possible toreduce an amount of nickel leaching into tap water from the device forwater supply to no more than one-tenth of the value defined in thetarget-setting item for water quality management.

Note that the present invention is not limited to the embodimentdescribed above, but encompasses modifications and improvements madewithin the range in which the object of the present invention can beachieved.

For example, equivalent effects are exerted by application of thepresent invention to a device for water supply including a nickelplating layer having no chrome plating layer formed thereon. The body ofthe device for water supply may be subjected to lead removal treatmentas necessary.

EXAMPLES Examples 1 to 5 and Comparative Examples 1 to 10

Bodies of devices for water supply of Examples and Comparative Exampleswere produced according to plating condition Nos. 1 to 15 shown in.

TABLE 1 Amount of Amount of Example/ Added Added Chloral ComparativeSaccharin Hydrate Base Plating Example Condition (g/L) (g/L) SolutionExample1 Condition — 0.9 Semigloss Ni No. 1 Plating ComparativeCondition 5.0 1.0 Gloss Ni Plating Example1 No. 2 Example2 Condition —0.2 Semigloss Ni No. 3 Plating Example3 Condition — 0.4 Semigloss Ni No.4 Plating Examp1e4 Condition — 0.8 Semigloss Ni No. 5 Plating Example5Condition —  1.25 Semigloss Ni No. 6 Plating Comparative Condition 5.0 —Ultra-Gloss Ni Example2 No. 7 Plating Comparative Condition 5.0 — GlossNi Plating Example3 No. 8 Comparative Condition — 1.8 Semigloss NiExample4 No. 9 Plating Comparative Condition — 1.9 Semigloss Ni Example5No. 10 Plating Comparative Condition — 2.0 Semigloss Ni Example6 No. 11Plating Comparative Condition — — Semigloss Ni Example7 No. 12 PlatingComparative Condition 5.0 3.0 Gloss Ni Plating Example8 No. 13Comparative Condition — — Semigloss Ni Example9 No. 14 PlatingComparative Condition 5.0 5.0 Gloss Ni Plating Example10 No. 15

<EPMA Analysis>

The bodies of the devices for water supply of Examples and ComparativeExamples were each subjected to an analysis using an EPMA. FIG. 5A showsa representative result of the analyses of the condition Nos. 2, 7, 8,13, and 15 in which the plating solution contained saccharin. FIG. 5Bshows a representative result of the analyses of the condition Nos. 1, 3to 6, 9 to 12, and 14 in which the plating solution did not containsaccharin. FIG. 6A shows, on an enlarged scale, the peak of sulfur inFIG. 5A. FIG. 6B shows, on an enlarged scale, the peak of sulfur in FIG.5B.

As shown in FIGS. 5 and 6, the condition Nos. 2, 7, 8, 13, and 15correspond to the so-called gloss nickel plating containing a sulfurcomponent added thereto. The condition Nos. 1, 3 to 6, 9 to 12, and 14correspond to the so-called semigloss nickel plating containing nosulfur component. In comparison with the gloss nickel plating, thesemigloss nickel plating, which contains no sulfur component, allows asmaller amount of nickel to leach.

<Appearance Observation>

Surfaces of the devices for water supply produced under condition Nos. 1to 15 were visually observed. Among the devices for water supply,devices that were as glossy as or glossier than the device for watersupply of the condition No. 8 (gloss nickel plating; Comparative Example5) are marked with a circle (“∘”). The devices for water supply of thecondition Nos. 12 and 14 (semigloss nickel plating containing no chloralhydrate) were not glossy, and the devices for water supply of thecondition Nos. 9 to 11 had a tarnished surface. These devices for watersupply were marked with a cross (“x”). A triangle (“Δ”) denotes devicesfor water supply having an intermediate degree of gloss between thosemarked with the circle (“∘”) and those marked with the cross (“x”).Further, the surface of each device for water supply was measured withthe WaveScan of BYK Japan KK. A relationship between the appearance andthe Wa value is shown in FIG. 7.

As shown in FIG. 7, it has been confirmed that the gloss of the surfaceof the body 10 for water supply increases with a decrease in the Wavalue of the surface of the device 100 for water supply. Specifically,it has been confirmed that when the Wa value is 5.1 or less, the glossof the surface is high enough so that device for water supply has anappearance suitable as a product. Further, it has been confirmed thatwhen the Wa value of the surface is 3.6 or less, the device for watersupply has gloss comparable to that of the gloss nickel plating.

<Ni Leaching Value and Corrosion Potential>

The devices for water supply produced using the Ni plating of thecondition Nos. 1, 2, 5 to 8, and 12 were each subjected to the followingconditioning and leach test in conformity with the method described inJIS S 3200-7 “Equipment for water supply service—Test methods of effectto water quality”.

(1) The device for water supply was washed with tap water for 1 hour,and then, washed with water three times.

(2) A leach test liquid at a temperature of about 23° C. was prepared.The inside of the device for water supply was filled with the leach testliquid and hermitically sealed. After the device for water supply wasleft standing for 2 hours, the liquid was disposed of. This operationwas repeated four times.

(3) The device for water supply was filled with the leach test liquidand hermitically sealed. After the device for water supply was leftstanding for 16 hours, the liquid was disposed of.

(4) The operations (2) and (3) were repeated three times.

(5) After the operation (2) was performed, the device for water supplywas left standing for 64 hours, and then, the liquid was disposed of.

(6) The operations (2) to (5) were performed once more.

(7) The operations (2) to (4) were repeated three times, and thereafter,the operation (2) was carried out.

(8) The device for water supply was filled with the leach test liquidand hermitically sealed. The device for water supply was then leftstanding for 16 hours, and all of the liquid was collected as a sampleliquid.

(9) A Ni concentration in the sample liquid was determined using acommon inductively-coupled plasma emission spectrophotometry.

(10) A calculation was performed using the Ni concentration of thesample liquid and a capacity of the tested device for water supply, sothat the Ni concentration was converted to a Ni concentration in 1 L ofwater and a leaching value was determined. Note that the leach testliquid used in the leach test was specially prepared according to JIS S3200-7.

By way of the operations described above, a nickel leaching value wasdetermined for each of the nickel plating layers produced under thecondition Nos. 1, 2, 5 to 8, and 12 (Example 1, Comparative Example 1,Examples 4 and 5, and Comparative Examples 2, 3, and 7). Note that sincethe different types of devices for water supply have differentcapacities, the leaching values were calculated according to apredetermined conversion formula. Subsequently, the following operationswere carried out.

(11) A specimen was cut off from an inner portion of the body 10 of thedevice for water supply where the Ni plating was deposited. Acopper-coated wire was bonded to the specimen, and then, the specimenwas coated with an adhesive such that only the Ni plating was exposed,whereby specimen was formed into a sample electrode.

(12) The sample electrode, a platinum electrode (counter electrode), anda saturated calomel electrode as a reference electrode were placed inthe leach test liquid. A potential-current curve of the sample electrodewas determined using a potentiostat. Here, a potential at which acurrent of 0.001 mA was observed was defined as a corrosion potential.

By way of the above-described operations, a corrosion potential in theleach test liquid was determined for each of the plating layers of thecondition Nos. 1, 2, 5 to 8, and 12 (Example 1, Comparative Example 1,Examples 4 and 5, and Comparative Examples 2, 3, and 7). FIG. 8 showsthe potential-current curves and the Ni leaching values of the platinglayers of Examples 1, 4, and 5, and Comparative Examples 1 to 3 and 7measured in the leach test liquid. FIG. 9 shows a relationship betweenthe corrosion potential and the nickel leaching value of the platinglayers of Examples 1, 4, and 5, and Comparative Examples 1 to 3 and 7measured in the leach test liquid.

As shown in FIG. 8, it has been confirmed that the nickel leaching valuedecreases with an increase in the corrosion potential of the nickelplating layer. Specifically, it has been confirmed that when thecorrosion potential is −0.01 V (with respect to the SCE) or greater, andpreferably +0.02 V (with respect to the SCE) or greater, the nickelleaching value is reduced to lower than that of semigloss nickel platingthat contains no chloral hydrate. Further, it has been confirmed thatwhen the corrosion potential is +0.04 V (with respect to the SCE) orgreater, the amount of nickel leaching into tap water from the devicefor water supply can be reduced to no more than one-tenth of the valuedefined in the target-setting item for water quality management.

EXPLANATION OF REFERENCE NUMERALS

-   100: Device for Water Supply-   101: Base Material-   102: Nickel Plating Layer

1. A device for water supply comprising a nickel plating layer formed ona base material, wherein the nickel plating layer contains no sulfurcomponent, wherein a corrosion potential of the nickel plating layer ina leach test liquid is −0.01 V or greater with respect to a saturatedcalomel electrode as a reference, and wherein a surface of the nickelplating layer has a Wa value of 5.1 or less as measured by BYK wave scandevice.
 2. The device for water supply according to claim 1, wherein thecorrosion potential of the nickel plating layer in the leach test liquidis +0.04 V or greater with respect to the saturated calomel electrode asthe reference.
 3. The device for water supply according to claim 1,wherein the corrosion potential of the nickel plating layer in the leachtest liquid is +0.02 V or greater with respect to the saturated calomelelectrode as the reference.
 4. The device for water supply according toclaim 1, wherein the surface of the nickel plating layer has a Wa valueof 3.6 or less.
 5. The device for water supply according to claim 2,wherein the surface of the nickel plating layer has a Wa value of 3.6 orless.
 6. The device for water supply according to claim 3, wherein thesurface of the nickel plating layer has a Wa value of 3.6 or less. 7.The device for water supply according to claim 1, wherein the sulfur isnot detected in an elementary analysis using an EPMA.
 8. The device forwater supply according to claim 2, wherein the sulfur is not detected inan elementary analysis using an EPMA.
 9. The device for water supplyaccording to claim 3, wherein the sulfur is not detected in anelementary analysis using an EPMA.